1. Technical Field
The present invention relates to a method and system for battery-based activation of a voltage regulator. The present invention more particularly relates to a voltage regulation method and system that is activated based on a battery voltage signal.
2. Description of the Related Art
Voltage regulation systems for controlling the field current of a diode-rectified alternating current generator, which supplies the electrical loads on a motor vehicle, generally are well known to those skilled in the art. One known type of voltage regulator senses the voltage applied to the battery, and if this voltage is higher than a desired regulated value, a transistor that controls field current is switched off. When generator voltage drops below the regulated value, the field controlling transistor is switched on. The transistor is repetitively switched on and off in response to sensed voltage changes to thereby cause the output voltage of the generator to be maintained at a predetermined, desired regulated value.
In another type of known voltage regulator, the field current is pulse-width modulated at a constant frequency to maintain the output voltage of the generator at a desired regulated value. In this type of regulator, the pulse width is a function of the difference between actual generator output voltage and a desired voltage. Examples of this type of regulator are disclosed in U.S. Pat. No. 2,976,473 to Shaw et al. and U.S. Pat. No. 4,275,344 to Mori et al. British Patent No. 1,392,096 also discloses pulse-width control of field current, and in that patent, the voltage reference takes the form of a cyclic staircase waveform.
Another example of a voltage regulator that employs pulse-width modulation of generator field current is disclosed in U.S. Pat. No. 4,636,706 to Bowman et al., the contents of which are incorporated herein by reference. According to Bowman et al., the regulator disclosed in that patent utilizes a digital apparatus that includes an up-down counter which responds to the relative magnitudes of the actual output voltage of the generator and the desired regulated output voltage of the generator. When the actual output voltage of the generator is below the desired regulated value, the counter is incremented or counted up, and when the actual output voltage is above the desired regulated value, the counter is decremented or counted down. The instantaneous count in the counter is used to determine the on time of a semiconductor switch that is connected in series with the field winding of the generator. The instantaneous count thus determines the pulse-width of the voltage that is applied to the field. Whenever actual output voltage exceeds the desired regulated value, the field controlling semiconductor switch is biased off. Thus, during the time that the actual output voltage is above the desired regulated value, the field is not energized and the counter is decremented. When actual output voltage then drops below the desired regulated value, the field is energized at the pulse-width represented by the magnitude of the count in the counter, and the counter is incremented.
Regardless of which type of voltage regulator is implemented, it is desirable to turn off the voltage regulator associated with an engine whenever the engine is not running. This prevents the energy stored in the engine""s battery from being drained by the regulator""s circuitry.
The voltage regulator, however, must be reactivated when the engine is started (i.e., when the generator begins to turn). One conventional way of reactivating the voltage regulator is to wire a vehicle""s ignition switch or other circuitry associated therewith to an activation input terminal (i.e., the lamp input) of the voltage regulator. In particular, this wiring is performed so that the voltage regulator gets xe2x80x9cstrobed onxe2x80x9d by closure of the ignition switch. This wiring arrangement, while generally effective, does require an electrical connection from the ignition switch or its associated circuitry to the voltage regulator. However, this added connection has some disadvantages. Since the connection extends out from where the regulator and/or generator is mounted, the connection remains relatively unprotected and susceptible to damage. The connection can be inadvertently disconnected, cut or otherwise rendered inoperative. The soldering techniques that are typically used to effect the added connection also can fail. If any of these events occur, the voltage regulator typically cannot become activated. As a result, no voltage regulation is provided and/or the generator fails to generate current. In the automotive context, this translates into added costs associated with repair and/or warranty work.
Consequently, there is a need in the art for a method and/or system capable of activating a voltage regulator in such a way that no external connection to an ignition switch is required, thereby reducing the likelihood that the voltage regulator will fail to become activated in response to the starting of the engine.
Another conventional technique for activating a voltage regulator avoids the external connection to the ignition switch by using the residual magnetism in the vehicle""s generator. In particular, one or more of the phases from the generator is connected to the lamp input (or another suitable input) of the voltage regulator and the residual magnetism from the associated winding is used to activate the voltage regulator when the generator begins to turn. The residual magnetism, however, can dissipate over time (e.g., through diode leakage in the bridge rectifier of the generator). This dissipation can result in turn-on problems for the generator. Similar problems arise when road salt or other contaminants invade the bridge rectifier of the generator. The residual magnetism-based arrangement therefore tends to be unreliable in some respects. In addition, disassembly of the generator and re-assembly requires the voltage regulator to be xe2x80x9cflashed,xe2x80x9d since there is no residual magnetism left in the windings after re-assembly of the generator. Such an arrangement also requires xe2x80x9cflashingxe2x80x9d when it is initially assembled.
Consequently, there is a need in the art for a method and/or system adapted to minimize or eliminate one or more of the shortcomings set forth above. In particular, there is a need in the art for a method and/or system adapted to activate a voltage regulator without requiring a connection to an engine""s ignition switch or related components, and also without requiring the presence of residual magnetism in the windings of the generator during an engine start.
One object of the present invention is to overcome one or more of the foregoing and other problems.
One advantage of the present invention is that unlike in conventional systems, it requires no additional connections external to the regulator. Another advantage is that no additional electrical inputs are required for regulator activation. The present invention provides a method adapted to activate a voltage regulator in response to a battery signal. This method begins by taking a measurement of the voltage signal provided by the battery. When the value of the battery voltage signal is below a threshold reference value indicative of when an engine is being started, then an activation signal is generated. The activation signal is applied to a voltage regulator to thereby commence regulation.
In a preferred embodiment, a field current through a field winding of a generator is strobed. Once strobing has begun, if the engine is rotating (and hence also the generator), the generator will produce an output (due to the active field current) and regulation begins.
A system for battery-based activation of a voltage regulator is also presented.